Wave-signal receiver



March 2l, 1950 J. J. OKRENT WAVE-SIGNAL RECEIVER Original Filed Oct. l5, 1944 *AMAA IN VEN TOR.'

E u R Y K E O N. R J m R tive receiver.

Patented Mar. 21, 1950 2,501,185Vv Y WAVE-SIGNAL RECEIVER f Jasper J. Oki-ent, Great Neck, N. Y., assgnor, by v mesne assignments,V to Hazeltine Research,

Inc., Chicago, Ill., a corporation of Illinois Original application October 13, 1944, Serial No.

558,531. Divided and this application November 9, 194:5, Serial No. 627,732

6 Claims.

This invention is directed to a wave-signal receiver ofv the superregenerative type including an arrangement for effectively disabling the receiver in response to an abnormal variation of ar rial Nc. 558,531., nled october 13, 1944, newv abandoned, in the name of Jasper J. Ofkrent and assigned to the same assignee as the present invention.

A superregenerative` receiver comprises a regenerative circuit in which the degree of regeneration 4provided is `such as to support oscillations, but the generated. oscillations are periodically suppressed by an applied periodic quench signal. The superregenerative receiver has numerous applications, one of which Will be particularly described. y

Consider, as an example, a Wave-signal transpondor system which includes a superregenera- The term Wave-signal transpondor system is here used to designatea Wavesignal translating system having a receiver portion and a transmitterV portion arranged to transmit a reply signal in response to a received inter# rogating signal, each such signal preferably comprising a pulse-modulated radiant-energy signal. Usually, the transmitter is triggered, orset into operation, under the control` of the receiver through an amplitude-selective circuit.v Tol obtain optimum sensitivityV of the transpondor system, a gain-control arrangement is'used to stabilize the receiver gain to a vcompromise value between that corresponding to maximum receiver sensitivity and that Whichis necessary to assure freedom from triggering the transmitter on the quiescent signal output of the receiver.

An operating limitation ofthe superregenerative receiver which may prove to be undesirable in such an installation concerns its quench-signal source. Under certain unavoidable conditions, notably as a result of a defective tube, the quench-signal supply may become disabled. Depending upon the adjustment of the superregenerative circuit, the loss of quench signal may provoke self-quenching of the receiver circuit, a condition in which the regenerative circuit periodically oscillates freely, the oscillations being quenched by self-blockingv in the oscillatory circuit. For the most part, self-quenching repre- I sents an uncontrolled operating state and may therefore be objectionable.

It is an object of the invention, therefore, to provide a wave-signal receiver of the superregenerative type having a quench-signal source and (Cl. Z50-20) which avoids the aforementioned limitation of prior art arrangements through an arrangement for effectively disabling the receiver in vresponse to an abnormal variation of a predetermined operating condition of its quench-signal supply.

t is a speciiic object ofthe invention to provide a Wave-signal receiver of the superregenerative type having a quench-signal source and including an improved arrangement for effectively disabling the receiver in response to a failure of its quench-signal source.

In accordance Withy the invention, a Wavesignal receiver of the superregenerative type lincluding an arrangement for effectively disabling the receiver in response to an abnormal variation of a predetermined 'operating condition thereof comprises means for supplying to the receiver a periodic quench signal for controlling superregeneration and having amplitude levels within a predetermined range of values during normal operating conditions, but having abnormal amplitude levels outside of this range of values in response to an abnormal variation of the aforesaid operating conditions. The receiver ff also includes a control system responsive pri-l marily only to these abnormal amplitude levels of 'the quench signal for deriving a control effect vention, together with other and further objectsn thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope'will be pointed out in the appended claims.

`Referring now more particularly to the drawing, the transpondor system there represented includes a superregenerative receiver, in accord'- ance with the present invention, and an associated Wave-signal transmitter. This system is substantially the same as that disclosed in Fig. 2 of the above-mentioned copending application Serial No. 558,531, corresponding components thereof being designated by similar reference characters. In the following discussion, the system as a Whole will be considered as a radio beacon adapted to transmit direction-finding infor,- mation to inquiring aircraft.

As illustrated, the receiver portion of the beacon comprises a superregenerative circuit including a triode vacuum tube l0 having anode, cathode and control electrodes. 1n the oscillatory circuitv of tube lllis a resonant circuit provided by the parallelpcombination of an inductor Il and an adjustable condenser I2. The resonant circuit is coupled to the anode and control electrodes of tube I by way of condensers I3 and I4, respectively. Regeneration is obtained in a conventional manner by coupling the cathode of tube I0 to a tap of inductor I I. An operating bias potentialfis applied to the control electrode of tube l0 from a source indicated --By through signal-frequency chokes I and I6. A source olf space current is applied to the tube in a manner to be pointed out hereinafter. i

There also is associated with the oscillatory circuit of tube IIJ means for supplying thereto 'a periodic quench signal for providing and controlling superregeneration. This means comprises an oscillation generator including a vacuum tube 'I0 arranged in an oscillatory circuitI of `the Hartley type. The oscillator has a frequency-determining circuit including an inductor 1I and an adjustable condenser l2, coupled to the control electrede of tube 'I0 through a condenser 'I3 and grid resistor-1`4. ,The anode of tube 'I0 is effectively connected with the `frequency-determining circuit by means of a condenser 15, while lthe cathode thereof is directly coupled to` a tap on inductor 1I. 'A source ofspace current, indicated +B, is applied tothe. anode of the tube and the quer;zh-,signal,outputY is derived in the cathode circuit for application to oscillator I0 through a condenser 16 and choke I6. As is well understood in the art, the oscillator is self-biasing through means comprising condenser I3 and its grid resistor 14.

, The quench signal supplied by oscillator 'I0 may have a sinusoidal or other suitable wave form, but has a frequency which is low with reference to the operating frequency of oscillator I I). Also, the quench frequency is high in ycomparison with thepulse-repetition frequencies of interrogating signals to be received by the beacon, preferably, beingso high that the quench period is equal to or lessfthan the pulse duration of a received signal. Chokes I5 and I6 are selected to isolate the oscillations generated in the receiver circuit from the bias potential ,-B and from the quenchsignal oscillator. q y y -condenser 20 couples a diode detector 2| to the described superre'generative circuit. The load circuit -of the diode Aincludesa signal-frequency choke 24 rand a resistor 22, icy-passed by a condenser 23. f .y

l The receiver also comprises again-stabilization channel, which includes a pulse ampliiierZS of one or more stages, coupled to the load circuit of diode 2| through a` signal-frequency' choke 3|. Following the pulse amplifier 29 in this channel is an automatic gain-stabilization or A. G. S. amplifier 30 of one or more stages.. The A. G. S. amplifier may include selector circuits'arranged to select a portion of the detected signal output oi the receiver for utilization in stabilizing the receiver gain.

There is coupled to the output circuit of A. G. S. amplifier 3D means for deriving from the gainstabilization channel a control signal having amplitude levels determined by the gain characteristicof the receiver. This means comprises an A. G. S. rectier, including a diode rectifier 40, coupled to the output circuit of A. G. S. ampli- -sistor 42.

nitude of the anode-cathode excitation potential of tube I0 is adjusted by the gain-stabilization arrangement. To this end, the signal output of rectifier 40, as obtained across its load resistor 42, is applied with positive polarity to the input circuit of an amplifier including a vacuum tube 32. An adjustably xed "component of bias potential is obtained from a bleeder network provided by a resistor and a voltage divider 45 connected in circuit with a suitableA potential source indicated -B. This bias potential is applied tothe input circuit of tube 32 through re- The magnitude of this bias potential is selected of such value that, in the absence of a controlv signal from A. G. S. rectifier 40, tube 32fis biased substantially to anode current cutoff. A source' of space' current, indicated +B, is coupled to the anode of tube 32. A unidirectional potential, having a magnitude determined by the conductive state of tube 32, is derived from the anode-cathode vcircuit thereof vand is 'utilized as the anode-cathode excitation potential for receiverftubeIUfFor'f this purpose, the anodes of tubes 32 andlll are coupled through a resistor 33"'andf'a filter` provided by series inductors 34 and 35 and shunt condensers 36 and 31. This arrangement *provides la source of space current fr" tube I0. l I

An'aiitenna'ground system 65, including'aninductor 66 inductivelycoupled with resonant'circuit II, `I2,' applies received signals `to the rece'ivr for translationtherethrough. 'Y

The receivern also ,has means for applying received wave signals translated therethrough to a utilizing circuit. `This lmeans comprises a repeaterfincluding' a vacuum -tube 50,' having an input circuit coupled to the output circuit of pulse amplifier 29. A source o'f' space current,

indicated +B, is coupled to the anode electrode of er y3Il through a condenser 4I. The load circuit of diode 40 is provided by a resistor 42, ya lter resistor 4,1 vand a byrpassA condenser43. The rectier circuit has a fastcharging time constant and a slow discharge time constantso as to peak rectifyr the vapplied signal output'ioft amplifier 30,.

'In stabilizing the gain of the receiver the magtube50. lDuring normal operating conditions, a screen-voltage of sufficient magnitude to operate tubef50 substantially above anode current cutoff is applied through a bleeder network of resistors 5I 'and 52 coupled to a potential-'source +B. The outputmcircuitof'repeater 5U is connected through .af/condenser' 53rtqfa'suitable utilizing circuit 54. The utilizing 'circuit 54, represented in block form, includes a pulse transmitter which is normally in al quiescent state but Which may be set into operation through an associated amplitudeselective trigger circuit to transmit a single pulse of a reply signal. The output circuit of unit 54 is'coupled to an antenna system 8U, BI for radiating the reply signal, and its input circuit is coupled through repeater l50 to the output circuit of pulse amplifier "29, as indicated'hereinabove. By virtue of l the interconnection'fbetween pulse amplifier 29 andtunitj54, the-operation 'of-the transmitter is controlled bythe superregenerative receiver. I y l; I

l'fThe receiver 'illustrated also comprises a control system for, effectively disabling the receiver in response toi'an abnormal variation of a predetermined operating condition thereof. This systemv constitutes means responsive to abnormal amplitude levels of the quenchsignal for deriving a Vcontrol effect, and includes an electrondischarge device shown as a triade amplifier including a vacuum tube 53.' The input circuit of tubei3 is coupled througha resistor 64 to the self-biasing arrangement pf the quench-signal generatonso asvito. be [biased lsubstantially to anode' current cutoff Vthereby during normal c )peratinyg'y conditions Iof the quench-signal generator. Abnormal variations of the operating conditionsof the quench-signal generator are effective to render tube 63 conductive, so that a control voltage is derived at its anode electrode. The output circuit of tube 63 is connected in shunt relation to resistor and the screen electrode of repeater 50 with respect to ground.

Finally, the receiver is shown as having additional amplitude-selective means, responsive to abnormal amplitude levels of the control signal derived by A. G. S. rectifier 40, for effectively disabling the receiver. This last-named means comprises a second electron-discharge vacuumtube device or triode amplifier 63 also having its `anode-,cathode circuit connected in shunt relation to resistor 5| and the screen electrode of repeater 5l] with respect to ground. Tube 6|] is normally biased to anode current cutolf by va suitable. bias potential B coupled to the input circuit thereof through a variable resistor 6|.

A resistor B2 couples the input circuit of tube 6|] to the output circuit of amplier 32 in order that tube til may be rendered conductive in response to adnormal amplitude levels of the control signal derived from A. G. S. rectifier 60. That is, tube 60 is rendered conductive in response to an adnormal variation in the gain condition of the A. G. S. system.

In operation, the circuit of receiver tube I0 is initially adjusted for sustained oscillations. During quiescent operating conditions when no signal is intercepted by antenna system 65, oscillations are periodically produced by oscillator I0 under the control of the quench voltage supplied by 'oscillator 1G. These oscillations are intiatecl by the low amplitude noise signal and similar `disturbances inherent in the receiver circuit and produce in the output circuit of detector 2| a. quiescent signal output. In response to this quiescent signal output, the gain-stabilization .system produces in the load circuit of rectifier 40 a control signal having amplitude levels determined by the gain characteristic of the receiver and included within a given range of values during normal operating conditions thereof.

This output signal of the A. G. S. rectifier 40 is applied with positive polarity to the input cir- `cuit of vacuum tube 32 and, in conjunction with :the biasing arrangement thereof, determines the `conductivity of the tube and consequently the lmagnitude of the unidirectional potential obtained therefrom and applied to the anodecathode circuit oi oscillator I0. The circuit adjustments are Asuch that, under normal conditions of operation, the excitation potential thus applied to oscillator I!! has that value which is required to establish optimum sensitivity of the receiver. The gain-stabilization system controls the receiver gain to maintain such optimum condition through appropriate variations of the anode-cathode excitation potential of tube I0.

The anode-cathode potential applied through the resistor 33 and filter elements 34 and 35 to receiver tube is likewise applied to tube 60, and under normal voperating conditions the latter remains at anode current cutoff. With tube 60 in a nonconductive state and the quench signal .circuits operating normally as discussed hereinbelow, normal operating potentials are established for repeater 59, rendering the repeater conductive to translate the signal output of pulse amplifier 29 to utilizing circuit 54.

For the assumed normal operating conditions ofthe receiver, control tube 63, as well asl tube 6l), is biased to anode ,current cutoff. With both control tube 63 and tube ,69 ina nonconductive state, repeater 50 is enabled to connect pulse amplifier 29 to utilizing circuit 54. Therefore, the quiescent signal output of the receiver is also applied to its utilizing circuit 5t. However, during normal operating conditions the controlled amplitude of the quiescent signal output is insufficient to excite the trigger circuit of unit 54 and trigger its associated transmitter.

Assume now, that an aircraft desiring direction-finding information from the beacon transmits thereto a pulse-modulated interrogating signal. This signal will, in general, have ahigh intensity with reference to the noise signal of the receiver circuit, wherefore oscillations generated in the receiver in any quench cycle occurring within the duration of the received pulse have a relatively high amplitude. During intervals which intervene between pulses of the received signal, the signal output of detector 2| comprises the quiescent signal output mentioned above. Hence, in response to the received interrogating signal, the output signal of detector 2| has high amplitude and low amplitude signal components, the former representing the modulation of the received signal. This signal output is translated through the gain-stabilization channel for the purpose of maintaining the desired receiver gain, in the manner indicated. This output signal is likewise applied through pulse amplifier 29 and repeater 50 to unit 54. The rst high-amplitude signal component derived from each received pulse of the interrogating signal causes the trigger circuit of unit 54 to excite its associated transmitter for the transmission of a reply signal. Therefore, in response to a received interrogating signal, the beacon transmits a pulse-modulated reply signal having the same pulse-repetition frequency as the received signal and having a pulse duration determined by the adjustments of unit .54. The inquiring aircraft is able toobtain the desired bearing indication or other direction-finding information from such transmitted reply signal.

Coming now to a consideration of the function of the control tube 63, this tube is adapted effectively to disable the receiver in response to an abnormal variation in the operating condition of its quench-signal generatol1 1l). During intervals in which this generator functions properly, the quench-signal output and the self-generated operating bias have amplitude levels within predetermined ranges of values. However, when the oscillator fails, the amplitude levels of the quench signal and the self-bias potential have abnormal values outside of their normal ranges of values, specifically, veach falls to zero. The loss of bias potential renders tube B3 conductive, thereby deriving a control effect from abnormal amplitude levels of the quench signal. As tube 63 conducts, the screen voltage of repeater 5e is reduced to a value which effectively drives the repeater to anode current cutoff, effectively disabling the receiver by disassociating its utilizing circuit 54 therefrom. Thus, under the control of control tube 63, the circuits associated with tube 50 constitute means for utilizing the control effect derived from abnormal amplitude levels of the quench signal effectively to disable the receiver.

Repeater 5i! conveniently may serve an additional purpose in the circuits illustrated, as will be pointed out in connection with the function of tube B0. Let it now be assumed that a failure has occurred in the gain-stabilization system', as may be occasioned vthrough a defective tube. kUpon such failure, thersignal derived from A. CnS.

atomes rectifier' H0 has an abnormal amplitude level outside of its normal range of values. Usually, a failure in the gain-stabilization channel causes the signal output of A. G. S. rectifier '40 to fall to zero. Thereupon, tube 32 is biased to anode current cutoff through its biasing circuit including voltage divider 46, raising the anode-cathode potential of tube I to an abnormally high level. As a result, the amplitude level of the quiescent signal output of the receiver may increase sumciently to trigger the transmitter of unit A54. However, a corresponding potential increase occurs in the input circuit of tube 60, rendering this tube conductive to establish a substantial shunt around resistor I and the screen electrode of repeater 50. Unit 54 is thereby eiectively disassociated from the receiver in the manner already described. By isolating unit.54, any invcrease in the am'plitude of the receiver quiescent signal output which may follow a failure in the gain-stabilization system has no undesirable effect on the transmitter of unit 54. Therefore, false firing of the transmitter is obviated. Thus, repeater 5U serves for effectively disabling the receiver in response to abnormal amplitude levels of at least one of the signal outputs of the quench generator and the gain-stabilization system. The control arrangement for disabling the receiver in response to a failure causing an abnormal operating condition of the gain-control system is particularly described in the above-mentioned copending application Serial No. 558,531.

It will be understood that control tube 63 and tube SD m'ay, if desired, be utilized to bias receiver tube I0 to anode current cutoff in the event of a quench signal or A. G.v S. failure. While this result may obviously be obtained with the described control arrangement, it may be more desirable in particular installations to utilize a modified form of control arrangement particularly described in copending application Serial No. 558,532, now Patent No. 2,467,564, rissued April 19, 1949, filed concurrently with the application Serial No. 558,531 mentioned above, in the name of Jasper J. Okrent, and assigned to the same assignee as the present invention.

While there have been described what are at present considered to be the preferred embodim'ents of this invention, it will be obvious to those skilled in the art that various changes and modiications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall Within the true spirit and scope of the invention.

What is claimed is:

l. A Wave-signal receiver of the superregenerative type including an arrangement for effectively disabling said receiver in response to an abnormal variation of a predetermined operating condition thereof comprising, means for supplying to said receiver a periodic quench signal for controlling superregeneration and having amplitude levels lWit-hin a predetermined range of values during normal operating conditions thereof but having abnormal amplitude levels out-- side of said range of values in response to an abnormal variation of said operating conditions, a control system responsive primarily only to said abnormal amplitude levelsof said quench signal for deriving a control effect, and means for utilizing said control effect effectively to disable said receiver.

2. A Wave-signal receiver of the superregenerative type including an arrangement for eiectively disabling said receiver in vresponse to an abnormal variation' of a predetermined operating condition thereof comprising, means for supplying to said receiver a periodic quench signal for controlling superregeneration and having amplitude levels Within a predetermined range of values during normal operating conditions thereof but having abnormal amplitude levels outside of said range of values in response to an abnormal variation of said operating conditions, a control system including an electron-discharge device biased substantially to anode current cutoff during normal operating conditions of said quench-signal supplying means but responsive to said abnormal amplitude levels of said quench signal for deriving a control effect, and means for utilizing said control effect effectively to disable said receiver.

3. A wave-signal receiver of the superregenerative type including an arrangement for effectively disabling said receiver in response to an abnormal variation of a predetermined operating condition thereof comprising, means for supplying to said receiver a periodic quench signal for controlling superregeneration and having amplitude levels within a predetermined range of values during normal operating conditions thereof but having abnormal amplitude levels outside of said range of values in response to an abnormal variation of said operating conditions, a control system including an electron-discharge device biased substantially to anode current cutoff by said quench-signal supply means during normal operating conditions thereof but responsive to said abnormal amplitude levels of said quench signal for deriving a control effect, and means for utilizing said control effect effectively to disable said receiver.

4. A Wave-signal receiver of the superregenerative type including an arrangement for effectively disabling said receiverin response to an abnormal variation of a predetermined operating condition thereof comprising, means for supplying to said receiver a periodic quench signal for controlling superregeneration and having amplituole levels Within a predetermined range of values during normal operating conditions thereof but having abnormal amplitude levels outside of said range of values in response to an abnormal variation of said operating conditions, a control system including an electron-discharge device biased substantially to anode current cutoff by said quench-signal supply means during normal 0perating conditions thereof but responsive to said abnormal amplitude levels of said quench signal for deriving a control voltage, means including a vacuum-tube repeater operated substantially above anode current cutoff during normal operating conditions of said receiver for applying signals translated therethrough to a utilizing circuit, and

means responsive to said control voltage for biasing said repeater to anode current cutoff, thereby effectively to disable said receiver.

5. A Wave signal receiver of the superregenerative type including an arrangement for eiectively disabling said receiver in response to an abnormal variation of a predetermined operating condition thereof comprising, a vacuum-tube -oscillation generator for supplying to said receiver a periodic quench signal for controlling superregeneration and including self-biasing means effective to provide an operating bias potential for said generator having amplitude levels Within a predetermined range of values during normal operating conditions thereof but having abnormal amplitude levels outside of said range of values in response to an abnormal variation of said operating conditions, a control system responsive to said abnormal amplitude levels of said operating bias potential for deriving a control effect, and means for utilizing said control effect effectively to disable said receiver.

6. A wave-signal receiver of the superregenerative type including an arrangement for effectively disabling said receiver in response to an abnormal variation of a predetermined operating condition thereof comprising, a vacuum-tube oscillation generator for supplying to said receiver a periodic quench signal for controlling superregeneration and including self-biasing means effective to provide an operating bias potential for said generator having amplitude levels Within a predetermined range of values during normal operating conditions thereof but having abnormal amplitude levels outside of said range REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,096,625 Brown Oct. 19, 1932 2,414,992 Wheeler Jan. 28, 1947 

